The holdout juror in the Lindsay Clancy trial did something that should be impossible in a functioning democracy: he admitted reasonable doubt, then refused to act on it. “I didn’t have any doubts” about her criminal responsibility, he told reporters, even as he acknowledged the defense’s psychiatric evidence created precisely the doubt the law requires. Eleven jurors voted not guilty by reason of insanity. One juror — Michael Desronvil, a 32-year-old Boston resident — stood alone, not because he disagreed with the evidence, but because he would not let the evidence change his verdict. The Clancy case was never really about one woman’s psychosis. It was a stress test for the jury system itself — and the system failed. Not because it produced the wrong outcome, but because it revealed that the deliberative ideal at the heart of Anglo-American justice has been hollowed out by the same forces rotting every other...